Two fundamentally different metabolic processes are used by most organisms:
respiration and fermentation. Respiration is aerobic, which means that it
requires oxygen, whereas fermentation takes place in the absence of oxygen
(i.e., it is anaerobic). Anaerobic bacteria dwell in places without oxygen
and produce methane. All of the oxygen in Earth's atmosphere was produced by
another group of photosynthetic aerobic bacteria about 2.4 billion years ago.
Until then, anaerobic methanogenic bacteria dominated the planet. With the
production of massive amounts of oxygen by these new photosynthetic bacteria,
Earth's atmosphere was changed and aerobic metabolism via respiration became
possible, ultimately leading to the evolution of eukaryotes and metazoans,
including vertebrates like ourselves, all of which require oxygen to survive. However, these
derived life forms also continue to exploit the process of fermentation alongside respiration.

Like carbon dioxide, methane is a greenhouse gas which
holds in heat. One molecule of methane is equivalent to about 25 molecules of carbon
dioxide in terms of its effects on global warming. When a molecule of methane burns,
it gives off heat and is oxidized into 2 molecules of water and one of carbon dioxide,
both of which are powerful greenhouse gases. Long frozen fossil methane is being
released from thawing permafrost and from the deep oceans at an ever accelerating
rate. Atmospheric carbon dioxide reacts with sea water to produce carbonic acid
which acidifies the oceans. Acidification of sea water inhibits formation of calcium
carbonate which interferes with the ability of calcareus oceanic phytoplankton such
as foraminiferans to lay down their tests. Ocean temperatures are also warming.
Ocean warming and acidification also causes corals to lose their mutualistic endosymbiotic
zooanthellae, resulting in the so-called "bleaching" of coral reefs. Combined with
overfishing, marine ecosystems worldwide are perilously close to collapse
(Domino Effect).
People simply do not appreciate the extent to which life on land depends upon healthy
ocean ecosystems, which are vital drivers of climate.

As temperatures rise, more methane bubbles reach the surface and enter the atmosphere,
further raising temperatures in an ever increasing positive feedback loop. Is there a
critical "tipping point" at which the state of Earth's surface will change drastically,
and if, so, what is it and when will it be reached? Some experts think this tipping
point may already have been crossed.

Major oceanic methane vents are shown on the following map. Methane levels in the
atmosphere are now more than double the levels that they have been over the
last half million years (see graph below). This could well portend the onset
of a powerful positive feedback loop that will almost certainly lead to very
rapid global warming.

We should be doing everything we can to KEEP the methane locked up in Earth's crust
and frozen in the deep oceans. However, people seem to think we can live above the
laws of nature and can use all the energy we "need" and want.
Fracking
cracks deep rocks releasing methane produced by anaerobes much of which vents to the surface
and enters the atmosphere.
We are also deliberately extracting methane from ocean clathrates and BURNING it
for energy. Both fracking and clathrate mining release a lot of waste heat that
cannot be dissipated as well as adding more water vapor and carbon dioxide to the
atmosphere, further enhancing global warming. An international consortium involving
Canada, the US, Japan, India, and Germany is already extracting methane from
clathrates and burning deep sea methane off the north coast of Canada at
a place called Mallik. The US government supports many similar
"Gas Hydrate"
projects. Our voracious appetite for ever more and more energy accelerates the rate of
global warming.
These ill-fated efforts to use methane as fuel will only hasten climate change.
What fools we humans are!

This plot is based on air samples of known age dating back almost
half a million years taken from Antarctic and Greenland ice cores.
Temperature changes are plotted in red, CO2 in fuzzy
gray, and methane levels in black. These changes are caused by complex periodic
fluctuations in Earth's orbit and the inclination of its axis known as the
Milankovitch cycles. Global warming is
nothing new, human
activities have strongly impacted climate during the last
10,000 years -- the Sahara is a man-made desert, currently expanding, and
Australia has undergone massive aridification during the past four decades
(map).